In many technical fields, like chemistry, biology, medicine or environmental protection, fluids have to be analyzed, processed, or brought into reaction with each other. For this purpose, fluids are filtered, cooled, heated, decomposed, washed, pipetted, or treated by other procedures. Often, in order to prepare a fluid, it is necessary to go through a long sequence of fluid processing steps. Further, in many cases, large sets of different fluids need to be processed according to the same sequence or batches of the same fluid need to be processed in parallel. This may be time consuming, limit the throughput and be prone to errors occurring during the procedure.
Fluid processing is used, for example, in the field of extracting and/or purifying biomolecules like nucleic acids or proteins. For example, a widely known method of purifying biomolecules is based on the steps of generating access to the content of a biological sample (“lysis”), selective binding of components of the content of the biological sample to a solid support or carrier material (“binding”), removing unwanted components from the solid support or carrier material (“washing”), and eluting the component of interest (“elution”).
In order to allow for a selective adsorbing and desorbing in the process of biomolecules purification, filter elements made of, e.g., silica-gel have been developed that on the one hand are porous or matrix-like in order to allow a fluid to pass through the filter element, and that on the other hand have a surface to which the biomolecules bind in a specific or nonspecific process. In other purification procedures biomolecules are detained on filter elements simply by the principle of size exclusion. In either way, if a biomolecule, e.g. a nucleic acid containing fluid passes through the filter element, some or all of the content remains with the filter element while the rest passes through the filter element.
Further, in order to recover the biomolecule from the filter element, an elution fluid, e.g. nuclease-free water, is dispensed onto the filter element for desorbing the biomolecule. This way, the biomolecule of interest is eluted from the filter element to be collected in a collection tube. Such filter elements are often applied as membranes either implemented in single tubes having an inlet opening and an outlet opening, or in multiwell plates, and processed using centrifuges (“spin format”) or vacuum based apparatuses. Single tubes with an inlet opening and an outlet opening that have a membrane and that can be spun in a centrifuge are also known as columns, spin columns, or single spin columns.
In general, the advantages of centrifuge based procedures over vacuum based methods are higher purity, higher concentration and a lower potential of cross contamination. In general, the best results for the purification of biomolecules, with regard to quality and concentration can be achieved using single spin columns combined with high g forces (>10.000×g) as there is a minimum of cross contamination and a maximum recovery from the membrane. A drawback is the labor intensive manual handling of spin columns increasing the error proneness and the process time if different samples are to be treated or processed simultaneously. A higher degree of standardization and automation as well as a higher throughput can be achieved by using multiwell plate formats mostly at the cost of quality and/or quantity.
QIAGEN offers a wide range of purification protocols for different biomolecules from a variety of biological samples all based on the overall Bind-Wash-Elute principle by using different filter materials and devices as, for example, described in WO 03/040364 or U.S. Pat. No. 6,277,648. The commercially available product “QIAGEN QIAprep Spin Miniprep Kit” for example discloses a typical purification sequence and offers standardized QIAprep Spin columns and 2 ml collection tubes for use in a centrifuge, and several reagents and buffers.
There are several publications relating to the automated processing of fluids involving centrifugal steps. U.S. Pat. No. 4,344,768 describes a pipettor apparatus for automatically transferring accurate and precise multiple quantities of samples (e.g., blood serum) and reagent to the rotatable transfer disc of a centrifugal analyzer. EP 0 122 772 describes a chemical manipulator adapted to automate the analysis of liquids of a μl unit, such as a DNA sample. U.S. Pat. No. 6,060,022 describes an automated sample processing system including an automatic centrifuge device. GB 535,188 describes an apparatus for obtaining a plurality of working bucket angles at a given speed of rotation of a centrifuge. U.S. Pat. No. 5,166,889 describes a sampling system adapted for blood, wherein a plurality of sample tubes are positioned for ready access on a support wheel, EP 569 115 A3 describes a centrifuge-based device for preparing DNA, and U.S. Pat. No. 539,339 describes an integral biomolecule preparation device using a centrifuge.
Several apparatuses for the preparation of samples using centrifugation are commercially available. “GENTRA Autopure LS” (GENTRA) and “AutoGenflex 3000” (AutoGen) are automated systems with an integrated centrifuge for the isolation of e.g. DNA after precipitation without using filtration elements. “DNA-Spinner” (PerkinElmer), “Genesis FE 500” (Tecan) and Microlab STARplus (Hamilton) are examples for more open systems where a liquid handling instrument is combined with an automated centrifuge for the use of multiwell plates.
On the other hand, for example, the “BioRobot 3000/8000” (QIAGEN) can be used for the preparation of samples, e.g. nucleic acids, in a 96-well format using vacuum filtration whereas the “Fuji QuickGene 800” applies a low pressure filtration principle on single columns.
However, most existing integrated systems for an automated preparation of biomolecules from fluids applying centrifugation are designed for a preparation of only specific procedures. Other instrument setups comprising an automated centrifuge are optimized for high throughput preparations using multiwell filtration plates. A drawback of existing automation systems is their inability to process high quality preparation procedures based on spin-columns without manual interventions.